NASA
SP-4209 The Partnership: A History of the Apollo-Soyuz Test Project, Appendix B -Development of
Manned Space Flight, American and Soviet.
http://www.hq.nasa.gov/office/pao/History/SP-4209/appb.htm

NASA
SP-4209 The Partnership: A History of the Apollo-Soyuz Test Project.
http://history.nasa.gov/SP-4209/toc.htm

RussianSpaceWeb.com. http://www.russianspaceweb.com/index.html

The Vision for Space
Exploration. http://www.nasa.gov/mission_pages/exploration/main/index.html